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Vivek Nigam, Bounded memory Dolev-Yao adversaries in collaborative systems

TCS Oberseminar, 27.05.2011, 11 Uhr c.t.
Wann 11:15 12:15 27.05.2011
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Wo L109
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Vivek Nigam,
Bounded memory Dolev-Yao adversaries in collaborative systems
 
This paper extends existing models for collaborative systems. 
We investigate how much damage can be done by insiders alone, 
without collusion with an outside adversary. In contrast to traditional 
intruder models, such as in protocol security, all the players inside 
our system, including potential adversaries, have similar capabilities. 
They have bounded storage capacity, that is, they can only remember at 
any moment a bounded number of symbols. This is technically imposed 
by only allowing balanced actions, that is, actions that have the same 
number of facts in their pre and post conditions, and bounding the size 
of facts, that is, the number of symbols they contain. On the other hand, 
the adversaries inside our system have many capabilities of the standard 
Dolev-Yao intruder, namely, they are able, within their bounded storage capacity,
to compose, decompose, overhear, and intercept messages as well as
create fresh values. We investigate the complexity of the decision problem 
of whether or not an adversary is able to discover secret data. We show that 
this problem is PSPACE-complete when the size of messages
is an input bound and when all actions are balanced and can possibly 
create fresh values. As an application we turn to security protocol analysis and 
demonstrate that many protocol anomalies, such as the 
Lowe anomaly in the Needham-Schroeder public key exchange protocol,
can also occur when the intruder is one of the insiders 
with bounded memory.

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